A feeding apparatus has been employed, as an example, for a power seat slide apparatus for slidably moving an upper rail supporting a vehicle seat relative to a lower rail fixedly connected to a vehicle floor in a forward and backward direction (longitudinal direction) of the vehicle by a driving torque of a motor. In such power seat slide apparatus, a screw shaft is provided between the lower rail and the upper rail. The motor rotatably moves the screw shaft, thereby adjusting a position of the upper rail relative to the lower rail in the forward and backward direction of the vehicle.
As an example for disposing the screw shaft between the lower rail and the upper rail, a structure described below has been proposed. The screw shaft is fitted into a hole portion of a supporting bracket provided at the upper rail and is rotatably supported thereby. Then, a first nut is screwed onto the screw shaft from a front side (a front side in an axial direction of the screw shaft) of the hole portion of the supporting bracket, while a second nut is screwed onto the screw shaft from a rear side (a rear side in the axial direction of the screw shaft) of the hole portion of the supporting bracket. Then, the first and second nuts are fixedly connected onto the screw shaft by compressing an end portion of each of the first and second nuts. The first and second nuts slidably move relative to an inner surface of the hole portion of the supporting bracket. Therefore, the screw shaft is supported rotatably relative to the supporting bracket. Further, a feeding nut is fixed to the lower rail and is screwed onto the screw shaft. Thus, the upper rail slidably moves relative to the lower rail by the rotational movement of the screw shaft.
However, when a load is applied for compressing the end portions of the first and second nuts, the screw shaft receiving the load may be slightly deformed. In such a condition, a torsion is generated at the rotation of the screw shaft, and a smooth rotation of the screw shaft may accordingly be interfered.
Further, even with a slight dimensional error of the first and second nuts, the supporting bracket loosely moves in the axial direction (frontward and backward direction) of the screw shaft. Therefore, the smooth rotation of the screw shaft may be interfered.
A need thus exists for a feeding apparatus, which is not susceptible to the drawback mentioned above.